First-principles equations of state for simulations of shock waves in silicon - art. no. 214107

We have calculated a thermodynamically complete equation of state for silic on, based on ab initio predictions of the electron ground states and quasih armonic phonons, and incorporating phase transitions between crystal struct ures. The equation of state was in reasonable agreement with data on the sh ock Hugoniot. We also used the equation of state in continuum mechanical si mulations to investigate the splitting of a shock wave, caused by phase tra nsition from the diamond structure. Good agreement is observed, which can b e made exact by adjusting the ab initio results to account for the known ov erbinding effects of the local-density approximation. The predictions were consistent with recent transient x-ray diffraction data on silicon.